ABSTRACT - Up to recently, freshwater ecosystems were neglected in assessments of the global carbon cycle and considered merely as passive ‘pipes’ which transport carbon from the land to the oceans. This view has been challenged by an increasing number of studies showing that freshwater ecosystems may negate a substantial fraction of the carbon sink through carbon dioxide (CO2) and in particular methane (CH4) emissions and thus rather should be viewed as ‘reactors’ which process a large fraction of the terrigenous carbon. Most of our knowledge on freshwater CO2 and CH4 emissions to date derives from studies in tropical and boreal regions, while temperate freshwater ecosystems, and in particular large lakes, are understudied. This study is focused on lake Garda, the evolution of dissolved carbon dioxide (CO2) and methane (CH4) at two different sampling points of the lake, during a year-long study. Lake Garda is an oligo-mesotrophic subalpine lake, situated in northern Italy, with a surface area of 368 km2 and a maximum depth of 350 m. To our knowledge, no such other survey on dissolved CO2 were done after Salmaso et al. (1998) and no study on dissolved CH4. We expect a supersaturation of dissolved carbon dioxide of the lake compare to atmospheric concentration. We also expect a seasonal variability of carbon species (HCO3-, CO32- and H2CO3).